The present disclosure relates generally to vehicle drive systems including an encoder and to methods for detecting a malfunction of the encoder.
Encoders are often used in vehicle drive systems for motorized vehicles such as, for example, automobiles, motorcycles, tractors, motorized wheelchairs, and/or the like. The encoder may be used in combination with a DC electric motor to provide information or output on the rotation of the motor at a particular instant of time. This rotational information may then be used to calculate, for example, the operating speed of the motor.
During substantially normal operating conditions (i.e., when the motor is rotating), a malfunction of an encoder may, in some instances, be readily detected. For example, for encoders with quadrature, loss of a single output channel while the motor is still rotating may still enable an operator to detect failure of the encoder by noting output pulses from another working channel. Loss of both channels of an encoder with quadrature while the motor is still rotating still enables an operator to detect a malfunction of the encoder. This is accomplished by noting that the rate of change in the calculated speed of the motor is substantially greater than a deceleration rate (i.e., the most aggressive operating deceleration) of the motor during the normal operating condition.
If the motor speed is controlled by a feedback speed control system, detection of a malfunctioning encoder is relatively important to minimize or prevent undesired drive wheel motion. Conversely, it is also relatively important to not incorrectly identify an encoder malfunction during a stalled motor condition.